him since, but shall soon, and will send you his sentiments. I am, Sir,

With great respect,

Your most humble servant,

B. FRANKLIN.

of the motions of the planets, and of the phenomena thereon depending, and of some other general phenomena, the causes of which, the author thinks, have not been before discovered."

The following extract from the Preface will exhibit to the reader an outline of Mr. Colden's views, and of the principles he attempts to establish.

"It is laid down as a principle, that all the primary or simple ideas we have of things external to us arise from the impressions or actions of these things on our senses; and, therefore, that the properties and qualities of things are nothing else but their various actions, or modes of acting, either simply or complicated; that the knowledge we have of things is no more than the perception of these actions, of their different degrees and different modes, and of the ratios of these differences to each other.

"That all simple beings or things have one single action, or manner of acting, essential to them; without which we have no conception of a thing.

"That there are two, and perhaps only two, essential different modes of action in material beings. The one, a power by which the thing, in which this action subsists, does resist all change of its present state; the other, a power by which the thing, in which the action of moving subsists, is continually changing its present state, or situation, by motion, and gives motion to every other thing, which at any time moves.

"It is a self-evident proposition, that nothing acts where it is not; therefore, if any thing exert any action at a distance, this action must be communicated to that distance, by some medium from the place of the acting thing, to the place where the action is communicated. The mutual apparent attraction of bodies at a distance from each other shows the necessity of the existence of such a medium. This medium makes a third kind of matter, essentially different from the other two, by its equally receiving the action, or manner of acting, either of the resisting or of the moving power, and by its reacting those actions with the same degree of force or action it received them. From the nature of this medium (commonly called ether), or from the necessary consequences of receiving and reacting these contrary modes of action, the apparent mutual attraction of bodies at a distance from each other, and gravitation, are explained, and the several phenomena thence arising.

"Every thing to which any action is essential, must exert that action equally in all directions; because nothing can be conceived in the thing

A Conjecture as to the Cause of the Heat of the Blood in Health, and of the Cold and Hot Fits of some Fevers.*

THE parts of fluids are so smooth, and roll among one another with so little friction, that they will not by any (mechanical) agitation grow warmer. A phial half full of water shook with violence and long continued, the water neither heats itself nor warms the phial. Therefore the blood does not acquire its heat either from the motion and friction of its own parts, or its friction against the sides of its vessels.

But the parts of solids, by reason of their closer adhesion, cannot move among themselves without friction, and that produces heat. Thus, bend a plummet to and fro, and, in the place of bending, it shall soon grow hot. Friction on any part of our flesh heats it. Clapping of the hands warms them. Exercise warms the whole body.

The heart is a thick muscle, continually contracting and dilating near eighty times in a minute. By this

itself to hinder it, in one direction more than another. Then the direction of motion in the moving power, towards any one point more than towards any other point, must be by something external, by the resistance in that particular direction being less than in any other.

"Several arguments are produced, in this essay, to demonstrate, that light is the substance or thing to which the power of moving is essential; and to those therein mentioned, among which the principal is the demonstrating in what manner the motions of the planets and cometa arise from thence, this other argument may be added, that we can have no conception of light without motion, of which any one may convince himself by a proper attention. For example, if light be supposed to be composed of small globular bodies at rest, this supposition gives no idea of light or colors; it conveys no idea of any thing in common with the deas raised in our mind by the action of light.". EDITOR.

This piece I have found in Franklin's handwriting among the papers of Cadwallader Colden. Its date is uncertain, but it was probably written before the year 1750. — Editor.

motion there must be a constant interfrication of its constituent solid parts. That friction must produce a heat, and that heat must consequently be continually communicated to the perfluent blood.

To this may be added, that every propulsion of the blood by the contraction of the heart, distends the arteries, which contract again in the intermission; and this distension and contraction of the arteries may oc casion heat in them, which they must likewise communicate to the blood that flows through them.

That these causes of the heat of the blood are sufficient to produce the effect, may appear probable, if we consider that a fluid once warm requires no more heat to be applied to it in any part of time to keep it warm, than what it shall lose in an equal part of time. A smaller force will keep a pendulum going, than what first set it in motion.

The blood, thus warmed in the heart, carries warmth with it to the very extremities of the body, and communicates it to them; but, as by this means its heat is gradually diminished, it is returned again to the heart by the veins for a fresh calefaction.

The blood communicates its heat, not only to the solids of our body, but to our clothes, and to a portion of the circumambient air. Every breath, though drawn in cold, is expired warm; and every particle of the materia perspirabilis carries off with it a portion of heat.

While the blood retains a due fluidity, it passes freely through the minutest vessels, and communicates a proper warmth to the extremities of the body. But when by any means it becomes so viscid, as not to be capable of passing those minute vessels, the extremities, as the blood can bring no more heat to them, grow cold.

The same viscidity in the blood and juices checks

or stops the perspiration, by clogging the perspiratory ducts, or, perhaps, by not admitting the perspirable parts to separate. Paper wet with size and water will not dry so soon as if wet with water only.

A vessel of hot water, if the vapor can freely pass from it, soon cools. If there be just fire enough under it to add continually the heat it loses, it retains the same degree. If the vessel be closed, so that the vapor may be retained, there will from the same fire be a continual accession of heat to the water, till it rises to a great degree. Or, if no fire be under it, it will retain the heat it first had for a long time. I have experienced, that a bottle of hot water stopped, and put in my bed at night, has retained so much heat seven or eight hours, that I could not in the morning bear my foot against it, without some of the bedclothes intervening.

During the cold fit, then, perspiration being stopped, great part of the heat of the blood, that used to be dissipated, is confined and retained in the body; the heart continues its motion, and creates a constant accession to that heat; the inward parts grow very hot, and, by contact with the extremities, communicate that heat to them. The glue of the blood is by this heat dissolved, and the blood afterwards flows freely, as before the disorder.

45817A

SIR,

TO PETER COLLINSON.

Magical Square of Squares.*

According to your request, I now send you the arithmetical curiosity, of which this is the history.

Being one day in the country, at the house of our common friend, the late learned Mr. Logan, he showed me a folio French book filled with magic squares, wrote, if I forget not, by one M. Frenicle, in which, he said, the author had discovered great ingenuity and dexterity in the management of numbers; and, though several other foreigners had distinguished themselves in the same way, he did not recollect that any one Englishman had done any thing of the kind remarkable.

I said, it was, perhaps, a mark of the good sense of our English mathematicians, that they would not spend their time in things that were merely difficiles nuga, incapable of any useful application. He answered, that many of the arithmetical or mathematical questions, publicly proposed and answered in England, were

The dates of the letters, in which the account of Magical Squares and Magical Circles was communicated to Mr. Collinson, are not known; but in a letter from James Logan to Mr. Collinson, dated February 14th, 1750, the following mention is made of them. "Our Benjamin Frankin," says Mr. Logan, "is certainly an extraordinary man, one of a singular good judgment, but of equal modesty. He is clerk of our Assembly, and there, for want of other employment, while he sat idle, he took it into his head to think of magical squares, in which he outdid Frenicle himself, who published above eighty pages in folio on that subject alone."

In reply to a letter from Mr. Logan on this subject, Franklin wrote (January 20th, 1749-50,) "The magical squares, how wonderful soever they may seem, are what I cannot value myself upon, but am rather ashamed to have it known I have spent any part of my time in an employment that cannot possibly be of any use to myself or others." EDITOR.